833
FXUS63 KDVN 281809
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
109 PM CDT Fri Jun 28 2024

.KEY MESSAGES...

- Off and on rain today with embedded thunderstorms. Question of
  whether or not we see strong to severe storms later due to
  slow returning instability.

- After a brief period of quiet weather this weekend, an active
  pattern sets up once again next week, with plenty of chances
  for showers and storms. Heavy rain is possible, but it is too
  soon to determine the severe threat.

- Moderate to Major flooding is expected on several area rivers.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 241 AM CDT Fri Jun 28 2024

A closed upper level low over Montana will drift southeast
towards the area today behind a quick moving shortwave this
morning. At the surface, high pressure will move east of the
area. This high helped to decrease deep moisture across the area
yesterday and early this morning. The leading shortwave, with an
attendant 30-35kt LLJ, is leading to widespread showers moving
into the area this morning. This jet is expected to continue in
some form this morning until the wave moves east of the area.
With limited CAPE, robust thunderstorms are not expected,
however, some rumbles of thunder are possible. This shower
activity is expected to continue during the morning hours
before gradually decreasing in coverage. Remarkably, the CAMs
are in good agreement in shower coverage and timing through the
morning, leading to a higher confidence forecast through at
least 18z.

In the afternoon, the stronger wave approaches the area. Deep
moisture return doesn`t occur til later in the afternoon. With
the showers from this AM, think cloud cover will keep the area
rather cool. As a result, think that CAPE will not be all that
impressive this afternoon and into the early evening.
Currently, think severe risk is very low across the area. That
said, deep layer shear is 30-40kts. If the forecast CAPE is
higher, and DMC occurs, there could be a chance for a strong to
severe storm as SPC depicts across our far west. The main thing
is CAPE, when does it get here, how warm do we get? We eventually
see MUCAPE build after sunset. The better chance for strong to
severe storms looks to be overnight, when shear increasing to
40-45 kts and CAPE moves into the area. Even then, we could have
so many small cores from the forcing that the severe risk could
be low. The main concern I see is heavy rainfall. Do not think
there is a flash flood threat. The main thing to me is what does
this additional rainfall do to the crest forecasts on area
rivers the next few days.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 241 AM CDT Fri Jun 28 2024

This weekend, we return to zonal flow aloft, becoming northwest flow
on Sunday, as a ridge builds over the Central US. Surface high
pressure will slowly traverse through the area during this time
period, exiting through the day on Monday. This timeframe will be
relatively quiet, weather-wise, which is welcomed. Saturday, we are
expecting temperatures to increase into the mid-upper 80s in our
southeastern half of the forecast area, with temperatures trending
near to slightly below normal Sunday and Monday. The warmer
temperatures Saturday will result from the slow-moving cold front
passing through the area that morning, allowing temperatures to warm
ahead of it. There will be a chance for showers and storms earlier
in the day, but as we approach the afternoon hours, we will see
chances drop off. From there, we will remain dry through Sunday and
much of Monday.

Monday night and into Tuesday, we see our first wave that is set to
impact the area this coming week. Much of the action with this seems
to be late Monday night, moreso during Tuesday morning, as the LLJ
takes much of the night to shift east over our area. Although, if
this system speeds up, we may see showers and storms earlier in the
night on Monday. This action will be associated with the leading
shortwave trough, with the bulk of the energy in our northern
forecast area. Thus, this will be the focus for higher
precipitation amounts and thunderstorm potential. It is too soon to
discuss deterministic amounts of rainfall, but we will see the
potential for heavier rainfall. Guidance is highlighting the
potential for high moisture content once again, with PWATs near 2.00-
2.50". Ensemble guidance remains quite low on probabilities for
rainfall, while deterministic guidance comes in quite aggressive
with precipitation. Thus, we will refrain from more details. Rather,
just be mindful that this can be a wet period, especially for those
in our northwest. The parent wave comes through Tuesday into
Wednesday, which will bring the chance for more heavy rain and
thunderstorms. As the cold front approaches that afternoon/evening,
moisture will pool along the boundary, with guidance highlighting
this being the timeframe with the highest PWATs. Thus, an increased
risk for higher rainfall rates.

Beyond that, guidance starts to diverge on the next system, with
large differences in timing and placement. While guidance seems to
favor the Thursday night into Friday timeframe for more precipitation,
will opt to refrain from any more details, as there is plenty of
time for this to change. In either case, it would seem that we will
approach the end of the work week with another round of showers and
storms for the area. All guidance highlights much of the end of the
week and into the weekend as an active period for rainfall.
Unfortunately, all of this rainfall will lead to further
fluctuations on the projected flooding along area rivers. Be sure to
stay up to date on local flood headlines!

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1240 PM CDT Fri Jun 28 2024

A disturbance moving across the area today as brought
widespread rain showers to the area with periods of MVFR
visibilities. We expect the showers to exit the area from west
to east from 21 to 00 UTC. Periods of MVFR to possibly IFR
conditions are possible in the most intense showers. There is a
low chance of thunderstorms this afternoon.

A small break in activity will occur late this afternoon into
this evening before another round of showers and storms develops
an impacts TAF sites from 03 to 09 UTC. There is lower
confidence on the coverage of these storms but if they do occur
MVFR to IFR conditions are possible. Conditions will quickly
improve after 09 UTC. Gusty northerly winds will develop after
12 UTC.

&&

.HYDROLOGY...
Issued at 1213 PM CDT Fri Jun 28 2024

Headline Changes:

Issued a flood watch for the Wapsipinicon River near De Witt due
to recent rainfall and QPF in the next 24 hrs. Upgraded Illinois
City LD 16 on the Mississippi from Moderate to Major flood
category.

Discussion:

Higher rainfall fell in the Wapsipinicon River basin than
initially forecast. As a result, the new forecast for the De
Witt gage has the river reaching flood stage in a little over 24
hrs. However, confidence in the placement of QPF tonight
remains too low to issue a warning at this time. Later shifts
will monitor trends and can issue if needed. The Cedar River
forecasts remain on track, with crests likely in the next 24
hours at Palo and Cedar Rapids. A secondary rise with a lower
crest than the 1st one, is now forecast on the Cedar due to the
1-2 inches that fell near the headwaters in the past 24 hours.

On the mainstem Mississippi, rises will continue at all sites
over the next 7 days. Higher rainfall amounts in southern MN
and northern IA in the past 24 hours has resulted in a quicker
forecast to Major flooding for many sites by approx. 36 to 48
hrs earlier, including Rock Island LD 15. Crests along the river
should begin to show up in upcoming forecasts this weekend
beginning with Dubuque LD 11. Barring any more heavy rainfall,
crests are anticipated in the July 4th-10th timeframe.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Gibbs
LONG TERM...Gunkel
AVIATION...Cousins
HYDROLOGY...Gross